The Atkins Diet is a popular low-carbohydrate eating plan developed in the 1960s by cardiologist Robert C. Atkins. The Atkins Diet restricts carbs (carbohydrates) while emphasizing protein and fats.

The Atkins Diet has several phases for weight loss and maintenance, starting out with a very low carbohydrate eating plan. The Atkins Diet, formally called the Atkins Nutritional Approach, has been detailed in many books and is credited with launching the low-carb diet trend.

The purpose of the Atkins Diet is to change your eating habits to help you lose weight and keep it off. The Atkins Diet also says it's a healthy lifelong approach to eating, whether you want to lose weight, boost your energy or help improve certain health problems, such as high blood pressure or metabolic syndrome.

Why you might follow the Atkins Diet

You might choose to follow the Atkins Diet because you:

Enjoy the types and amounts of food featured in the diet

Want a diet that restricts certain carbs to help you lose weight

Want to change your overall eating habits

Have medical concerns you think the diet can help improve

Like the related Atkins Diet products, such as cookbooks, shakes and bars

Check with your doctor or health care provider before starting any weight-loss diet, especially if you have any health conditions, such as diabetes.

The main dietary focus of the Atkins Diet is eating the right balance of carbohydrates, protein and fats for optimal weight loss and health. According to the Atkins Diet, obesity and related health problems, such as type 2 diabetes and heart disease, are the fault of the typical low-fat, high-carbohydrate American diet. The Atkins Diet says that you don't need to avoid fatty cuts of meat or trim off excess fat. Rather, controlling carbs is what's important.

The Atkins Diet holds that eating too many carbohydrates — especially sugar, white flour and other refined carbs — leads to blood sugar imbalances, weight gain and cardiovascular problems. To that end, the Atkins Diet restricts carbohydrates and encourages eating more protein and fat. However, the Atkins Diet says it is not a high-protein diet.

Like many diet plans, the Atkins Diet continues to evolve. Now, it encourages eating more high-fiber vegetables, accommodates vegetarian and vegan needs, and addresses health problems that may arise when beginning a low-carb diet.

Carbohydrates

The Atkins Diet doesn't require calorie counting or portion control. It does require you to track your carbs, though. It uses a system called net carbs, which is the total carbohydrate content of an item minus its fiber content. For example, a half-cup (4 ounces) of raw broccoli has 2.3 grams of total carbs and 1.3 grams of fiber, putting its net carb value at 1 gram.

The Atkins Diet says its approach to carbs will burn off your body's fat stores, regulate your blood sugar and help you achieve optimal health, while not leaving you feeling hungry or deprived. Once you're at your goal weight, the Atkins Diet also says it will help you identify your personal carbohydrate tolerance — the number of grams of net carbs you can eat each day without gaining or losing weight.

Exercise

The Atkins Diet claims exercise isn't vital for weight loss. However, it acknowledges that exercise can help maintain your weight, as well as offer other health benefits.

Phases of the Atkins Diet

The Atkins Diet has four phases. Depending on your weight-loss goals, you can start at any of the first three phases.

Phase 1: Induction. In this strict phase, you cut out almost all carbohydrates from your diet, eating just 20 grams of net carbs a day, mainly from vegetables. Instead of getting 45 to 65 percent of your daily calories from carbohydrates, as recommended by most nutrition guidelines, you get only about 10 percent. "Foundation" vegetables, such as asparagus, broccoli, celery, cucumber, green beans and peppers, should account for 12 to 15 grams of your daily net carbs.

You should eat protein, such as fish and shellfish, poultry, meat, eggs, and cheese, at every meal. You don't need to restrict oils and fats, but you can't have most fruits, sugary baked goods, breads, pastas, grains, nuts or alcohol. You should drink eight glasses of water a day. You stay in this phase for at least two weeks, depending on your weight loss.

Phase 2: Balancing. In this phase, you continue to eat a minimum of 12 to 15 grams of net carbs as foundation vegetables. You also continue to avoid foods with added sugar. You can slowly add back in some nutrient-rich carbs, such as more vegetables and berries, nuts, and seeds, as you continue to lose weight. You stay in this phase until you're about 10 pounds (4.5 kilograms) from your goal weight.

Phase 3: Pre-maintenance. In this phase, you continue to gradually increase the range of foods you can eat, including fruits, starchy vegetables and whole grains. You can add about 10 grams of carbs to your diet each week, but you must cut back if your weight loss stops. You stay in this phase until you reach your goal weight.

Phase 4: Lifetime maintenance. You move into this phase when you reach your goal weight, and then you continue this way of eating for life.

A typical day's menu on the Atkins Diet

Here's a look at what you might eat during a typical day on phase 1 of the Atkins Diet:

Lunch. Chef salad with chicken, bacon and avocado dressing, along with an allowable beverage.

Dinner. Baked salmon steak, asparagus, and arugula salad with cherry tomatoes and cucumbers, along with an allowable beverage.

Snacks. You typically can have two snacks a day. Snacks may include an Atkins Diet product, such as a chocolate shake or granola bar, or a simple snack such as celery and cheddar cheese.

Weight loss

The Atkins Diet says that you can lose 15 pounds (6.8 kilograms) in the first two weeks of phase 1 — but it also acknowledges that those aren't typical results. The Atkins Diet also acknowledges that you may initially lose water weight. It says that you'll continue to lose weight in phases 2 and 3 as long as you don't eat more carbs than your body can tolerate.

Most people can lose weight on almost any diet plan that restricts calories — at least in the short term. Over the long term, though, studies show that low-carb diets like the Atkins Diet are no more effective for weight loss than are standard weight-loss diets and that most people regain the weight they lost regardless of diet plan.

Because carbohydrates usually provide over half of calories consumed, the main reason for weight loss on the Atkins Diet is lower overall calorie intake from eating less carbs. Some studies suggest that there are other reasons for weight loss with the Atkins Diet. You may shed pounds because your food choices are limited, and you eat less since the extra protein and fat keep you feeling full longer. Both of these effects also contribute to lower overall calorie intake.

Health benefits

The Atkins Diet says that its eating plan can prevent or improve serious health conditions, such as metabolic syndrome, diabetes, high blood pressure and cardiovascular disease. In fact, almost any diet that helps you shed excess weight can reduce or even reverse risk factors for cardiovascular disease and diabetes.

And most weight-loss diets — not just low-carb diets — may improve blood cholesterol or blood sugar levels, at least temporarily. One study showed that people who followed the Atkins Diet had improved triglycerides, suggesting better heart health. But there have been no major studies to show whether such benefits hold up for the long term or increase how long you live.

Some health experts believe that eating a large amount of fat and protein from animal sources, as allowed on the Atkins Diet, can increase your risk of heart disease or some cancers. However, it's not known what risks, if any, the Atkins Diet may pose over the long term because most of the studies about it have lasted for two years or less.

The Atkins Diet acknowledges that drastically cutting carbs in the early phase of the program can result in some side effects, including:

Headache

Dizziness

Weakness

Fatigue

Constipation

In addition, some very low carb diets restrict carbohydrates so much that they result in nutritional deficiencies or insufficient fiber, which can cause such health problems as constipation, diarrhea and nausea.

Eating carbs that are high fiber, whole grain and nutrient dense can improve the health profile of programs like the Atkins Diet, though. In addition, the Atkins Diet has changed over time to help prevent health problems, and it now recommends taking a small amount of extra salt, along with vitamins or supplements.

It's also possible that restricting carbohydrates to less than 20 grams a day — the level recommended for phase 1 of the diet — can result in ketosis. Ketosis occurs when you don't have enough sugar (glucose) for energy, so your body breaks down stored fat, causing ketones to build up in your body. Side effects from ketosis can include nausea, headache, mental fatigue and bad breath.

In addition, the Atkins Diet isn't appropriate for everyone. For example, the Atkins Diet recommends that you consult your doctor before starting the diet if you take diuretics, insulin or oral diabetes medications. In addition, people with severe kidney disease should not follow the diet, and the weight-loss phases of the diet aren't suitable for women who are pregnant or breast-feeding.

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